Study of dielectric properties of (PVCMWCNTs) Polymer nanocomposite

8/20/2019 Study of dielectric properties of (PVCMWCNTs) Polymer nanocomposite

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International Journal of Application or Innovation in Engineering& Management (IJAIEM)Web Site: www.ijaiem.org Email: [email protected]

Volume 4, Issue 12, December 2015 ISSN 2319 - 4847

Volume 4, Issue 12, December 2015 Page 43

ABSTRACT

Thermal pressure is one of the easiest methods fabricating polymers nanocomposites bulk. In this study the range of 5%, 10%,

15%, 20%, 25%, 30%, 35% and 40% of weight percentages of Multi walled carbon nanotube (MWCNT) were added to

polyvinyl chloride (PVC) powder . Final mixing of each of any concentration has pressured under temperature 80 C .

… Dielectric properties were measured at room temperature and different frequencies; it was found that the dielectric constant

increased with increasing the carbon nanotubes content, but decreasing with increasing frequency. This may be due to

polarization effects of the nanocomposite. Also the dielectric loss of polymer composites has been measured. The results refer that the dielectric loss isreduced with increasing of frequency and The A.C conductivity is increases with the increasing of the

concentration of Multi walled carbon nanotube because of the increase of the charge carriers and the formation of a

continuous network of Multi walled carbon nanotube inside the nanocomposites. .

Key words: dielectric constant, dielectric loss, AC conductivity, nanocomposites.

1.INTRODUCTION

Polymer composites can be defined as materials that consist of two or more chemically and physically different phases

separated by a distinct interface [1]. Many types of nanofiller can change not less one of important property when we

are adding to polymer like this nanofiller is carbon nanotube [2, 3, 4]. The development of nanotube, platelet and

particle reinforced polymer composites has grown in importance in recent years due to their attractive applications in

various fields. Two and three-dimensional nanofillers into a polymer matrix giving high aspect ratios and large surface

area to volume ratios [5].Materials that contain a polymer matrix with conductive filler are known as conductive polymer composites [6, 7] ....These composites are known for having high dielectric constants and for being extremely

conductive. This is achieved by the conductive filler forming a network throughout the composite which allows for the

flow of current through the composite. The conductivity of these composites can increase by several orders of

magnitude. Since the matrix consists of a polymer, these composites have the potential of increasing in flexibility, if the

polymer used in the matrix is flexible. The composite can be brittle and weak due to the amount of filler that is needed

to produce a highly conducting material. The main advantage of conductive polymer composites is that they display

characteristics of both a metal and of a polymer [6, 8].

2.PREPARATION METHOD

Multi walled carbon nanotube (MWCNTs) were supplied by Material and Electrochemical Research (MER)

Corporation, U.S.A,the diameter of (MWCNTs) was (140 ± 30 nm) and a length of (7 ± 2) microns.. It were mixed

with weight percentages (5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%) of Polyvinyl chloride (PVC) was supplied as a powder form by pars petrochemicalwith density 1.16 gm/cm

3 using an electronic balance of accuracy 10

-4 gm.Mixing

device was used to mix the (MWCNT) and polymer (PVC) for (3-5)minute to get more homogenous mixture, then it is

placed in a thermal mold and heated to( 100c). After that the mixture was cooled to 80c and compressed under

pressure(2000N/cm2) in the form of a disc with (2cm) diameter and (0.2) cm thicknessafter the sample cooling to 30c .

3.RESULTS & CONCLUSIONS

3.1 Dielectric constant

The dielectric constant (ɛ ), which is the most important for A.C properties, was calculated by using the equation (1)

which gives the ratio of the capacitance of a dielectric-filled capacitor (C p) to a capacitor of free space (C 0).

C

C

ε

p (1)

The dielectric constant is determined with various frequencies at room temperature.

Study of dielectric properties of (PVC-

MWCNTs) Polymer nanocomposite.

Asrar Abdulmunem Saeed, Batool Daram Balwa, Intisar Mohammed shatti

(College of science, Department of physics) University of AL-Mustansiryah / Iraq






Figures (1) shows the variation of the dielectric constant of (PVC-MWCNTs) nanocomposites with frequency. This

figure shows that the dielectric constant values decrease when the applied field frequency increases. The increase of

frequencies results in decreasing of space charge polarization (interfacial polarization) to the total polarization. The

space charge polarization becomes the more contributing type of polarization at low frequencies, and less contributing

with the increase of frequency; this would result in the decrease of dielectric constant values for all samples of (PVC-

MWCNTs) nanocomposites with the increase of the electric field frequency (f) [9].The other types of polarizations appear at high frequencies. The ionic polarization reacts slightly to the variation in the

field frequencies compared to the electronic polarization. This is because the mass of ion is greater than that of the

electron. The electrons respond to even the high frequencies of the field vibrations. The low mass of electron makes

the electronic polarization, the only type of polarization at higher frequencies. This makes the dielectric constant

approximately constant for all samples at high frequencies. The results agree with[10].

Figure (1): Variation of the dielectric constant of (PVC-MWCNTs) nanocomposites with frequency

The dielectric constant increases with the increasing of the concentration of Multi walled carbon nanotubes [11].

The reason for this increase in the value of dielectric constant is the formation of a continuous network of carbon

nanotube inside the nanocomposites; at low concentrations of additive like pure (0%), 5%, 10% and 15% take the

form of clusters or separated groups; hence, the dielectric constant becomes approximately low, and at high

concentrations like 20%, 25%, 30%, 35% and 40% form a continuous network inside the nanocomposites and because

increase (C p) for the storage charges, and so the value of dielectric constant increases with the volumetric rate of the

nanotube . The results agree with [12, 13].

3-2 Dielectric loss

The dielectric losses (ɛ ″) are calculated by followed equation (2):

ε

εtan δ

(2)

Where tan δ is loss factor.

The figure (2) represented to dielectric loss increases again until it reaches to the highestvalue at (f=100 Hz) of (PVC-

MWCNTs) nanocomposites.

This value represents the highest dielectric loss at certain frequency; that is the highest absorption of applied field. [14].

When the frequency (f) is increases to 3 kHz, the dielectric loss is approximately constant of (PVC-MWCNTs)

nanocomposites.

This is attributed to the mechanisms of other types of polarization that occurs at high frequencies. The value of

dielectric loss increases by increasing the concentration of nanotubes; thisis due to the increase of the charge carriers

caused by the increase of concentration of nanotube. The results agree with [11, 15].






Figure (2): Variation of the dielectric loss with frequency of (PVC-MWCNTs) nanocomposites

3-3 The A.C electrical conductivity

TheA.C electrical conductivityis calculated by followed equation (3)

εε.cσ A

(3)

where is the angular frequency of the applied field ( =2πf ).

Figure (3) shows the variation of the conductivity for PVC-MWCNT with frequency. The figure shows that AC

conductivity increases considerably with the increase of frequency (f) from 100HZ to 5*106 Hz. This is attributed to the

space charge polarization that occurs at low frequencies and to the motion of charge carriers by hopping process. Theincrease of the conductivity is small at high frequencies; this is attributed to the electronic polarization and the charge

carriers, which travel by hopping process [15]. Consequently, the conductivity is increasing when the frequency

increases for all different rates of (MWCNT) for PVC-MWCNT nanocomposities.

0

100

200

300

400

500

600

700

800

900

0 1 2 3 4 5

C o n d u c t i v i t y ( o h m . c m

) - 1

Frequncy (МHz)

pure * E-7

PVC:10%mwcnt *E-7

PVC:20%mwcnt*E-7

PVC:25%mwcnt *E-7

pvc:30%mwcnt*E-7

pvc:35%mwcnt*E-7

pvc:40%mwcnt *E-7

Figure (3): Variation of A.C electrical conductivity with frequency of (PVC-MWCNT) nanocomposites.





Volume 4, Issue 12, December 2015 6

Figure (4)shows the variation of A.C conductivity PVC-MWCNT nanocomposites, with Multi walled carbon nanotubes

concentration at 100 Hz under room temperature 30C . The A.C conductivity slightly increases at low concentrations

of the Multi walled carbon nanotube (MWCNT).This increase is due to the effect of the space charge. The Multi walled

carbon nanotube takes the form of clusters or separated groups.

The conductivity is increases with the increasing of the concentration of MWCNTsbecause of the increase of the charge

carriers and the formation of a continuous network of MWCNTsinside the nanocomposites. Consequently, theconductivity is increases with the increasing ofMWCNTs concentrationfor PVC-MWCNT nanocomposites. The results

agree with [11].

0

5E-10

1E-09

1.5E-09

2E-09

2.5E-09

3E-09

0 5 10 15 20 25 30 35 40

C o n d u c t i v i t y ( o h m . c m ) - 1

MWCNTs wt. concentration

Conductivity at f =100 (Hz)

Figure (4): Variation of A.C electrical conductivity with MWCNTwt. % concentration at 100 Hz of

(PVC-MWCNT) nanocomposites

3.4 conclusionsThe dielectric constant behaviors were decreasing with increasing of frequency and increasing with carbon nanotube

concentrations, this effect may be due contribute the polarization and form network inside the polymers, the dielectric

loss of the (PVC-MWCNTs) nanocomposites decrease with the increase of frequency of the applied electric field and

The A.C conductivity is increases with the increasing of the concentration of Multi walled carbon nanotube because of

the increase of the charge carriers and the formation of a continuous network of Multi walled carbon nanotube inside

the nanocomposites.

References

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AUTHOR

Intisar Mohammed received the B.S. and M.S. degrees in Applied physics from University of

Technology in 2005 and 2008, respectively. During 2011-2015, she studiedthe solid state physicsin Universityof ALMustansiriah In Partial Fulfillment to the Requirements for the Degree of

Doctor of Philosophy in Physics.

Study of dielectric properties of (PVCMWCNTs) Polymer nanocomposite

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